1. Field of the Invention
The present invention relates to flexible bearings and, more particularly, to improvements in continuous strip type flexible bearings and a method for making such bearings.
2. Description of the Prior Art
Flexible bearings made up of a plurality of alternate layers of rigid reinforcements and elastomeric pads are known in the prior art. Such bearings are disclosed in a number of U.S. Patents, as follows: U.S. Pat. No. 2,995,907 to M. Crain; U.S. Pat. No. 3,071,422 to W. L. Hinks; U.S. Pat. No. 3,390,899 to J. T. Herbert et al.; U.S. Pat. No. 3,429,622 to R. E. Lee et al.; U.S. Pat. No. 3,690,639 to W. D. Brandon et al.; U.S. Pat. No. 3,941,433 to W. T. Dolling et al.; U.S. Pat. No. 3,958,840 to C. C. Hickox et al.; U.S. Pat. No. 4,108,508 to R. L. Clinard, Jr.; U.S. Pat. No. 4,141,950 to A. R. Thompson; and U.S. Pat. No. 4,349,184 to R. R. Peterson.
When applied to thrust nozzles for solid propellant rocket motor nozzles, flexible bearings incorporating alternate layers of metal reinforcement and elastomer, irrespective of whether concentrically or spirally arranged, are commonly quite thick in order to contain enough elastomer to provide stable and controllable vectoring of the nozzle through shear deformation of the elastomer. Because of the tendency of thick layers of elastomer to be extruded between the metal reinforcement layers, the elastomer, conventionally, is divided into a large number of thin layers. This necessitates the use of a similarly large number of reinforcement metal layers which has added, undesirably, to the height and weight of the bearing.
Such an approach becomes less and less acceptable as the technology involved in the construction of rocket motors, particularly, advances and produces demands in terms of smaller size, specifically, decreased height and less weight, for flexible bearings capable of providing stable and controllable vectoring of the nozzle for steering the rocket.
In order to minimize flexible bearing height and weight, it is also known in the prior art to utilize therein lightweight, strong, thin, molded composite reinforcements. Structural requirements and manufacturing limitations for composite reinforcements, however, preclude the design of flexible bearings that truly operate at their ultimate capability. Present rocket motor nozzle configurations result in a compressive circumferential load that must be carried by the bearing and supporting structure. Thus, reinforcements have always had compressive stiffness and strength requirements. The present minimum thickness limit for composite reinforcements that meets the structural requirements has exceeded the limits of cost effective manufacturing, as evidenced by an unacceptable composite reinforcement rejection rate. Molded composite reinforcements are susceptible to voids, delaminations, and contamination.
Thus, there is a need and a demand for improvement in flexible bearings and the methods for making such bearings to the end of enabling minimization of bearing height and weight for a given amount of elastomer for shearing. The present invention was devised to fill the technological gap that exists in this respect.